A source close to the 34-year-old sisters tells PEOPLE that Brie was concerned that Nikki was “sacrificing” too much in the relationship.
“On one level, Brie wants to kill him, sure. No one should be allowed to hurt her sister like this. But honestly, on another level, there’s relief,” the source says. “Nikki was bending over backward to accommodate this guy and everyone, especially Brie, was worried that she was sacrificing way, way too much — most of all, motherhood.”
While Nikki publicly stated in the past that she was willing to give up being a mother for Cena, 40, those closest to the reality star knew she still struggled with the decision.
“The things she said when she was with John — that she didn’t need to be a wife, or then that she didn’t need to be a mom — that’s just not Nikki,” the source adds.
And after Brie gave birth to her first daughter Birdie in 2017, it became increasingly hard to watch her sister give up on her dream of starting a family.
“She will be such an amazing mom someday, and she loves Brie’s baby so much,” says the source. “So of course that’s what Brie wanted for Nikki. To have to hear her trying to convince herself and everyone else that she would be fine just giving it up, it was so hard. Brie never bought it.”
RELATED VIDEO: How John Cena ‘Convinced’ Nikki Bella That He Was a Changed Man Before Ending Engagement: Source
Cena and Nikki announced that they called off their engagement on Sunday, a year after he proposed during WrestleMania 33. The couple was scheduled to marry on May 5 during their planned destination wedding.
The source tells PEOPLE that Nikki’s family is optimistic that she will find someone who will be able to give her “everything she’s dreamed of.”
“There’s some relief that at least Nikki can go forward and find someone who will really give her everything she’s dreamed of,” the source says. “Because that guy isn’t John. Never was.”
Cena and Nikki’s relationship — as well as their discussions about marriage and kids — have been documented on the hit E! reality shows Total Divas and Total Bellas.
“I do want to be a mom,” Bella told Cena in 2013 on Total Divas. “I feel like I’d be missing out.”
“I’m going to choose my words carefully,” Cena replied. “I can’t give you that.”
Total Bellas returns May 20 at 9 p.m. ET on E!